Moles of many colours

Golden moles are burrowing mammals native to southern Africa that are completely blind. Yet, their fur produces "a rainbow of colours when viewed from various angles, much like the surface of a compact disc," according to Dr Kevin Rowe, Senior Curator of Mammals. This raises the question: why would an animal that lives in the dark, and can't see anyway, be brightly coloured? Kevin and his colleagues, including MV Research Associate Dr Karen Rowe, have published a new study in Biology Lettersthat considers the implications of how and why iridescence evolved.

Many insects, reptiles and birds use iridescence to attract mates, but this depends on keen eyesight on the part of the viewer. Analysis under scanning electron microscopy and transmission electron microscopy showed that the golden mole's colourful sheen is produced by the same mechanism as other animals: microscopic surface structures that refract light. The minute layers of scales on the surface of each hair are "most likely to reduce drag and damage while the moles swim through sand and soil," explains Karen. "The colours they produce are merely a by-product."

Hairs from these four golden mole specimens were analysed with scanning electron microscopy and transmission electron microscopy in this study.Source: Museum Victoria

The only other known example of mammal iridescence is the 'eye shine' seen when torchlight reflects from the retina of nocturnal animals, a useful trick for spotting animals in trees. With more investigation, the researchers may find other species with true iridescence and thus piece together the story of its evolution.